The roof-tops of commercial and industrial buildings are often used to support items such as pipes, HVAC components, cable trays, electrical conduits, walkways, and drainage systems. The items often need to be elevated above the surface of the roof-top to prevent damage to the roof.
Most commonly, pipes need to be supported above the roof-top. Some of these are for condensate drains for roof-top HVAC systems. Other pipes are used for roof-top drainage, or for steam and liquids, or even as electrical conduits. Because the roofs often have uneven surfaces, the pipes are raised above the roofs and are supported at regular intervals to prevent them from sagging. The supports are especially important at junctions, couplings, and turns because stress at these junctures is more likely to result in a leak.